The non-polar molecular nature of the olefin-based polymers (for example, olefin multi-block copolymers) makes them difficult to be bonded, painted, and printed due to the low surface energy of these polymers. For example, in the footwear assembling process, the midsole is bonded to the vulcanized rubber outsole, and to the shoe upper which is made from natural/artificial leather. Typically, the existing maximum total olefin-based polymer loading in the midsole formulation cannot exceed 30 wt % (the balance is EVA), due to adhesion issues of higher olefin content of the olefin-based polymer content compositions. Therefore new adhesion formulations are needed, which provide acceptable bonding performance of midsoles containing higher amounts of olefin-based polymer. In previous foam laminates, UV primers were developed to enhance the bonding of “olefin rich” foams to other substrates, using PU adhesives. For example, see WO2016004898, which discloses disclosed a UV primer for OBC rich midsole bonding, by using reactive diluents, maleic anhydrate grafted chlorinated polyolefins, styrene block copolymers, photo initiators and solvents; and International Patent Application No. PCT/CN16/076245 (filed Mar. 14, 2016), which discloses a novel bonding process to further improve the bonding strength of OBC rich midsole foam by increasing the UV energy but still maintain the OBC foam sample non warped (due to the unique block structure of OBC). Other polymer formulations, most or all curable by UV, are described in the following references: U.S. Pat. Nos. 6,225,369, 6,653,394, 7,388,039, US20090018231 and WO2010016075.
However, there is still a requirement for high green peel strength as the bonded shoe product will be subjected to compression and transportation in a short time. A high green peel strength will ensure the bonded sample will not delaminated during these post treating steps, which is very important to ensure the production quality. This need has been met by the following invention.